U.S. Pat. Nos. 5,119,994 and 4,974,781 are incorporated herein by reference.
Rising concerns regarding proper handling and disposal of waste materials continues to occur. One serious waste disposal problem is that of medical waste materials that can harbor infectious agents and diseases. Incidents of medical waste materials washing ashore along the coastlines and of bags of medical waste materials being dumped in ditches strike fear into the hearts of all people, causing an outcry for better controls.
Public opinion has caused activity by legislators and regulators, particularly at the federal level, concerning the management of medical wastes. The Environmental Protection Agency (EPA), the Office of Technology Assessment (OTA), the Center for Disease Control (CDC) and the Occupational, Safety and Health Act (OSHA) have issued management guidelines and regulations regarding medical wastes including the Medical Waste Tracking Act.
Medical wastes that potentially harbor infectious agents have been identified by the OTA as being generated by hospitals, clinics, doctor's offices, dentist's offices, veterinarian's offices, mortuaries, laboratories and other medical and research facilities. Recognized options for handling and managing these wastes include incineration, microwaving, autoclaving, chemical treatment, hydropulping and land disposal. A large percentage of hospital generators in the United States use or have access to some type of combustion system to incinerate these wastes.
Combustion of medical wastes has the unfortunate effect of releasing pollutants into the air. Of primary concern is the release to the atmosphere, from the medical waste combustors, the pollutants of hydrogen chloride (HCl), sulfur dioxide (SO2), particulate matter (PM), trace organics such as dioxins and furans, arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), and others. Many of the combustion systems that are in service do not adequately control these pollutants and are a cause for concern. This concern has been addressed by Section III of the Clean Air Act (CAA), and these regulatory standards may preclude the use of medical waste combustion at many installations by requiring extensive control measure to be added to combustion facilities.
Medical waste generation rates have increased substantially in the past twenty years. The increase is believed due to factors such as the increasing use of disposable materials and the redefinition of the regulated waste fraction. As diseases such as AIDS receive increasing public attention, increasing pressure will be brought to bear on the generators of medical waste to the extent that anything that comes into contact with a patient or a patient's blood or bodily fluids will be classified and managed as being potentially infectious. This circumstance is called “Universal Precautions” by the CDC.
With such circumstances developing, hospital administrators attempt to balance their systems to minimize medical waste amounts that are potentially infectious and that are the most costly to manage, by having their staff segregate wastes in multiple containers within hospital rooms and operating rooms. This can lead to arbitrary decisions as to what is infectious and what is not, and places an additional burden upon a staff that often works under crisis conditions. The concern, of course, is that incorrectly classified material may be incorrectly disposed of. Incorrect disposal could result in violations of the regulations for management of these wastes with severe fines being levied on the violator or, in the worst case, be the cause of an outbreak of an infectious agent functioning to contaminate people. However, to practice no segregation of materials and to classify all waste as potentially infectious would be economically prohibitive to a generator.
In light of this growing dilemma, it has become appropriate to strive for the perfection of a method and an apparatus for the processing of medical wastes into ordinary, common wastes so that these wastes may then be managed for disposal or recycling in the commonly accepted general waste disposal system without the threat of the spread of an infectious agent.
Waste paper has been recycled and used as a source of feedstock for the manufacture of paper products. The availability of recycled paper, however, is subject to the economics of the recovery, sorting, and cleaning of the waste paper from the waste paper containing materials requiring sorting of the paper at the source of generation and special handling by the generator; dedicated pickup of specially segregated materials by a recycler; and component separation by the recycler after collection.
Waste plastics have become increasingly important because of their very long term resistance to degradation and decomposition in the environment and because of the hazardous nature of the gaseous compounds that are produced when plastics are incinerated. The recovery, sorting, and cleaning of waste plastics for recycling, as with waste paper, typically also requires sorting of the plastic at the source of generation and dedicated pickup of specific plastics by a recycler to be viable as a source of plastic to be utilized by the plastics industry.
It has long been recognized that the achieving of a method of separating waste paper and plastics from the extraneous contaminating components that typically accompany a paper containing waste material would be highly desirable. This is particularly true if the paper and plastic containing waste material is municipal solid waste. Municipal solid waste typically contains 25-60% paper materials along with a varying assortment of glass, metals, rags, food wastes, plastics, etc. It is believed that typical component compositions for municipal solid wastes are as follows:
TABLE 1Paper35.2%Metals8.0%Plastic11.3%Glass5.3%Food Waste11.7%Grass Clippings12.1%Wood5.8%Leather, Textiles,7.4%and RubberOther3.4%TOTAL100.0%
It is believed that much paper and plastic containing waste materials are being landfilled, resulting in the loss of paper and recyclable materials and the using up of valuable land space. Landfills also threaten the environment with contamination of surface and groundwater, and present health hazards and public nuisances by increasing numbers of disease-carrying birds, rodents and insects. The problem is an ever-increasing one. By their existence, municipalities and industries generate paper-containing and plastic-containing wastes continually and these wastes must be properly disposed of. Various approaches such as incineration, composting, and producing refuse-derived fuel have been considered as alternative solutions to landfills.
Incineration, although it can reduce the amount of landfilling required, produces undesirable and hazardous pollutants released in the air, primarily by the combustion of plastics contained in the waste materials and the volatilizing of metals such as aluminum contained therein. Incineration also produces relatively few products generating revenue except for energy sales of steam and electricity, which are dependent on adjacent customers and subject to rates set by local public utilities, causing most of the costs related to incineration facilities to fall on the public attempting to deal with the waste streams.
Composting, which is the process of subjecting waste materials to microbial action to produce a soil-like material is believed to have potential only as a soil conditioner. Because it contains relatively little nutrient value, compost cannot compete as a fertilizer. Additionally, the concentration of heavy metals in compost may be unacceptable considering that these will be absorbed into plants, and up the food chain.
Producing refuse-derived fuel from waste materials requires that a series of steps be taken to separate combustible materials from non-combustible materials. Separation results in several classification processes, producing a number of low quality products of limited value. The refuse-derived fuel produced contains plastics which produce undesirable and hazardous pollutants released to the atmosphere when combusted.
Because of problems inherent in present methods of waste disposal, the continuing need to dispose of waste materials, and the need to recover valuable products currently being lost, there is a need to provide improved methods of separation and recovery of component fractions from waste paper and plastic containing materials.
While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.”